Self-sharpening plow share



`NGN- 17, 1931-. l s. s. SHERMAN ETAL 1,832,429

SELF SHARPENING PLOW SHARE Filed NOV. 11, 1926 ,readily than the hard steel layer,

Patented Nov. 17, 1931 UNITED STATES PATENT ola-FICE GEORGE BENJAMIN SHERMAN AND ROBERT HENRY '.POTTS, OF EVANSVILLE, INDIANA,

ASSIGNORS, BY DIREGT AND MESNE ASSIGNMENTS,

KENT CORPORATION, OE EVANSVILLE, INDIANA, A CORPORATION OF INDIANA SELF-SHABPEN ING SHARE Application led November 11, 1926. Serial No. 147,705.

The present invention relates to a novel self-sharpening plow share, comprised of two or more layers of steels having different carbon contents.

One of the greatest objections to present day plow shares is ened frequently, thereby involving loss of the life of the share. This applies particularly to tractor plow shares when used in hard ground in the fall of the year, sincel under these conditions the shares must be resharp'ened almost levery day.

The primary object of the present invem tion, therefore, resides in the provision of a novel plow share which can be left on the plow without being resharpened until it wears out, or at least until it has given considerable service.

object of the invention is to rovide a novel plow share which will be sel -sharpened by use.

Still another object is to provide a new and improved self-sharpening plow share which is inexpensive in con struction, and easy to manufacture, which is strong and tough, and in which the surface subjected to the severest wearing action is hard and smooth and therefore not likely to collect pasty soil or to be roughened by the scouring action of the soil.

We accomplish the above objects by pro- A more speciiic viding a plow share consisting of two layers of steel, one of which has a high carbon content and is heat and the other of which has a low carbon content, and has therefore a relatively high ductility. The hard steel layer preferably is made the upper layer of the share where most of the scouring action of The soft steel layer, being tough and ductile, backs up and reenfnrces the more brittle hard layer so as to protect the latter against breaking or cracking when striking hard objects in the soil or when used under severe conditions. This soft layer, being adapted to wear more will, as wear occurs. always recede a short distance from the relatively sharp edge'of the latter, thereby providing the plow share at all times that they must be resharp- The share comprises treated to provide hardness,

the soil will occur.'

TO SHERMAN BROS. DEVELOP- with a sharp cutting edge regardless of wear. l

Further objects and advantages will become' apparent as the description proceeds.

VIn the accompanying drawings:

Fi re 1 illustrates a plow share of stand` ard esign which is constructed in accordance Y,with our invention. time, trouble, and expense, and shortening Figs. 2 and 3 are respectively fragmentary sections taken along lines 2-2 and 3-3 of Fig. l, and showing diagrammatically the thicknesses of the two steel layers of. different carbon contents. y

While our invention is susceptible of varions modifications and alternative constructions, we have shown in the drawings and will herein describe in detail the preferred embodiment, but it is to be understood that we do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

v Referring more specifically to the draw? point 6 having a cutting edge 7, said cutting one side of the share. an upper layer 8 and a one layer having a high carbon edge running along lower layer 9,

content and being hardened, and the other layer having a relatively low carbon content and being unhardened. Since most ofthe wearing action normally occurs against the Y top of the plow share. it is preferable to make the upper layerl 8 with the high .carbon;con tent and the lower layer 9 with the Vlow carbon content. It is also preferable that the vhigh carbon steel have from .80% to 1.00%

carbon, and that the low carbon steel have less than .25% carbon.

In making the plow share, the single ply of two layer steel may be obtained by either of two processes, namely: the rolling process or the carbonizing process. In the rolling process, two separateplies of steel having the desired carbon contents and the desired relative thicknesses are rolled together under heat and pressure to form a single ply. The resulting two layer ply is now annealed and cooled slowly to normalize the crystalline structure which was worked and hence distorted in the rolling.

In the carbonizing process, a single ply of steel having a uniform carbon content correspending to the desired low carbon content of the layer 9 is provided. This ply is subjected on one side or surface only to a carbonizing action to obtain the desired high carbon content of layer 8 to the desired depth. The demarcation between the layers preterably should be abrupt so that each layer is of sufficient thickness to accomplish its purpose. The carbonizing process is old and well known in the case-hardcning of metal parts, and it is therefore deemed unnecessary to describe the same herein. It is sufticient to say that the carbon content and the depth of the high carbon layer can be controlled by varying the conditions under which the process is carried on.

The two-layer ply oi steel, whether formed by the rolling process or by the oarbonizing process, is now formed into the desired shape et the plow share. Since the specific' means by which, and manner in which, this is accomplished are old and well known in the art, and torni no part ot the present invention...tl 1e v will not be described herein.

The plow share is now heat treated in a manner to harden the high carbon layer'S but toretain the low carbon layer 9 in a ductile and unhardened condition. When steel is heated through its critical range, the preersting crystalline structure, however coarse, is destroyed and a refined structure is obtained. The structure, which is finesty as it emerges from the range, will grow on turheating' and will continue to coarsen as it cools slowly to the critical range. The refined structure is hard and tough. No material refining of the structure, and hence no hardening will take place it the temperature ot' the steel remains below its critical point. in carrying out the heat treatment, the plow share is heated to a temperature at or slightly above the critical range of the high carbon laver, but not through the critical range of the low carbon laver. This is possible since in divergent carbon contents in hypo-eutec toid steels, the upper temperatures of the @ritieni ranges ot said steels diter considerably. Thus, the approximate upper critical temperatures for 0.85?. 0.40% and 0.20% carbon steels are respectively 7150 C., 770 il. and 81300 C. rtheoretically. to obtain the maximum hardness and toughness. the steel should be heated just through the critical range, and no higher. in industrial practice. however.l the plow share is heated to a temperature slia'htlv above the critical range so that the interior of the metal. which lags in temperature when the share is heated rapidly. will pass through the range, and so that there will Vbe time enough to handle the share readily,

before the temperature drops through the range on cooling. Preferably, the plow share is heated up to a temperature approximately between 760o C. and 825 C., the maximum temperature depending upon the percentage of carbon in the low carbon layer t). By heating the high carbon layer 8 above its critical temperature, its old crystalline structure is destroyed and. refined, thereby hardening the layer. layer 9 is not heated above its critical range, it is not hardened appreciably. Furthermore, low carbon steel, since it has more free ferrite than has high carbon steel, is softer and more .ductile than the latter even when heated throu h the critical range. Hence, it the layer 9 as a very low carbon content, it can even be heated above its critical range without hardening too much for the present purpose. As a result of the heat treatment, the layer 8 will be hard and will not wear and the layer 9 will be tough to prevent breakage in use, and will wear to leave the sharp edge of layer 8 exposed.

To retain the fine hard structure of the high carbon layer 8, the plow' share is quenched, thereby denying time for the structure to coarsen and soften, as it would if allowed to cool slowly to atmospheric teinperature. Preferably the quenching or annealing bath consists of brine" at or below a temperature of 10 C.

In quenching the plow share, there will be a tendency to warp, due to the excessive and uneven shrinkage of the high carbon layer 8 in cooling through its critical range, and further due to the difference in the coeiticients of shrinkage of the two layers. Uniform warpage can be controlled by making allowance therefore. Heretofore it has been found impossible to maketwo layer steel plow shares without excessive and irregular warpage. This warpage caused cracking, and sometimes breaking. The present invention contemplates making the. warpage as uniform as possible, and reducing it to a point where it can be easily and permanently corrected.

High temperatures in the heat treatment result in warpage. By heating the plow share only7 as tar above the critical range of high carbon layer 8 as necessary, increased warpage which would result from higher temperatures is avoided.

0n cooling, the hard layer 8, in passing through its critical range, will shrink considerably, while the layer 9, never having been heated through its own critical range, will shrink but. little and uniformly. If the layer 8 is sott. it can-yield and give, thereby preventing the shrinkage from causing excessive warpagc. lf. howe ver. the surface Vot' the laver 8 is hard before the interior reaches the critical range. as it will be if quenched when substantially above the critical range,

Since the low carbon fill the interior in shrinking from the unyielding exterior will cause excessive warping and will set up severe stresses. The higher the temperature is above the critical range when the plow share is uenched, the greater will be the warpage. ence, in carrying out the present invention, the plow share is quenched when the temperature is near or at the critical range of the layer 8, and preferably near the lower limit of the range. This', will cause more nearly uniform cooling, and

hence will greatly reduce warpage.

-The plow share should shrink uniformly in cooling from the critical range. To shrink uniformly, the plow share must be cooled uniformly. Invheating the plow share to high temperatures, the surface oxidizes very readily, and the scale of oxide, being a heat insulator, will, if not removed, prevent uniform cooling. Therefore, after the heat treatment, and just before the share is immersed in the quenching bath, the share is dropped or handled in some suitable Way to quickly remove the scale of oxide. To prevent oxidation and hence the formation of a heat insulating scale, the plow share may be coated with a layer of relative-ly non-oxidizing material, such as a very thin copper plate, before the heat treatment. Oxidization may be prevented to a substantial degree by making the plow share of chromium steel, the chromium also serving to produce a hardery steel. In this connection it is to be understood that. the soft layer 9 need only be soft enough te provide sucient toughness for preventing breaking of the share, and to wear more readily than the hard layer 8. y

To correct the slight warpage that may have obtained in the process thus far described, the plow share is quickly removed from the quenching bath when its temperature has fallen to a point slightly above that at which molecular action ceases, and is placed in a suitable shaping or forming press. Preferably this temperature ranges between 100o C. to 160o C. lf the plow share were removed from the bath at a substantially higher temperature, the layer 8 would temper or draw, thereby losing its hardness. It is deemed unnecessary herein to show the specific construction of the shaping or forming press, since the latter per se forms' no part of the present invention. The forming press with the plow share therein may be allowed to cool in the atmosphere` but preferably is immersed in a washing bath, such as a water bath, before the temperature has fallen to the point at which molecular action ceases, and is left in the bath until the plow share has cooled to a final temperature. after which no further 'arping can occur. The slight molecular change which occursafter the plow share is placed in the press serves to set the crystalline structure and to remove the stress which results from correcting the warpage.

As a result, a steel plow Itard layer and a soft layer, and being substantially umvarped` is obtained. le use, 'the upper layer 8 is subjected to nust of the wear, but being very hard and curable will wear slowly, and because of its union with' the soft layer 9 will not break readily, (fue to the ductility ot' the latter. As the s lare wears away, the wear ot the soft layer ll precedes that of the hardened layer so that the latter always presents a substantially sharpened edge. The plow share is smooth, hard, durable and sharp. The method of making the plow share causes the layer 8 tohave maximum hardness, and strength, causes the layer 9 to have maximum ductility and toughness, reduces warpage to a"mininunn, causes what warpa ge there is to be substantiallyy uniform, and permanently corrects that warpage without settin up stresses and without cracking the plow s are.

Vhile the invention is particularly applieableto plow shares and renders same selfsharpening, it willbe obvious that in its broad aspect it is applicable generally tol soil-,tilling members.

lille claim for our invention 1'. A. self-sharpening soil-tilling member comprisinf, in combination, a relatively high carbon hardened upper layer of steel having a relatively sharp cutting edge, and a ductile layer of steel underlying said first mentioned layer, the carbon content of the steel in said last mentioned layer being less than .25%.

Q. A self-sharpening soil-tilling implement comprising, in combination, a hardened layer of steel containing at least .8% carbon and having a relatively sharp edge, and a ductile layer of steel containing less than .25% carbon backing said first mentioned layer and receding slightly7 from the edge of said first mentioned layer.

3. An uuwarped self-sharpening plow share comprising, in combination, a relatively high carbon hardened upper layer of chromi- 'um steel having a fine crystalline structure and having a relatively the carbon content of said layer being from .8C2 to 1%. a ductile low carbon unhardened layer of steel thicker than and underlying said first mentioned layer and recedin slightly from said edge, said last mentioned laver having a carbon content of less than .25% and having a gunnel formed integral therewith, the line of den'larcation between said layers being substantially straight, the outer surfaces of both layers being smooth and uninterrupted. and a thin plating of copper on the exterior of said layers. i

l. .tu unwarped self-sharpening plow share comprising'` in combination, a relatively high carbon hardened upper layer of share. having a sharp cutting edge,

steel having a fine crystalline structure and having a relatively sharp cutting edge, the carbon content of said layer being from .8% to 1%, a ductile low carbon unhardened layer of steel underlying said first mentioned layer and receding slightly from said edge, the carbon content of said lastmentioned layer being less than .25%, the line of demarcation between said layers being substantially straight, the outer surfaces of both layers being smooth and uninterrupted, and a thin coating of non-oxidizing material on the exterior of said layers.

5. An unwarped self-sharpening -plow share comprising, in combination, a hardened upper layer of eutectoid steel having a fine crystalline structure and having a rel- 'atively sharp cutting edge, and a ductile low carbon unhardened layer of steel underlying said first mentioned layer and `recedin slightly from the edge of said first mentioned layer, the carbon content of said last mentioned layer being less than .25%, the line of demarcation between said layersl being substantially straight, the outer surfaces of both layers being smooth and uninterrupted.

6. An unwarped self-sharpening plow f share comprising, in combination, a rela- 'tively high carbon' hardened upper layer of chromium steel having a fine crystalline structure and having a relatively sharp cutting edge, and a ductile low carbon unhardcned layer of steel underlying said first mentioned layer, the carbon content of said last mentioned layer being less than .25%, the outer surfaces of both layers being smooth and uninterrupted.

7. A self-sharpening soil-tilling member comprising, in combination. a hardened upper laver of eutectoid steelv having a line crystalline structure and having a relatively sharp cutting edge, and a ductile low carbon unhardened layer of steel underlying said first mentioned layer and receding slightly from the edge of said irst mentioned layer, the outer surfaces of both layers being smooth and uninterrupted.

8. A self-sharpening soil-tilling member comprising. in combination, a relatively high carbon hardened upper layer of steel having a relatively sharp cutting edge. and a ductile layer of steel underlying said first mentioned layer, the carbon content of the steel in said last mentioned laver being less than .25%, said ductile layer being thicker than said hardened layer.

9. A self-sharpening soil-tilling member comprising. in combination, a relatively high carbon hardened upper layer of steel having a relatively sharp cutting edge, a ductile layer of steel underlying said first mentioned layer, the carbon content of the steel in said last mentioned layer being less than .25%, and a thin coating of non-oxidizing material on the exterior of said layers.

10. A. self-sharpening soil-tilling member comprising, in combination, a relatlvel high` 

